Darwin Correspondence Project

<On alteration> in the structure of Lychnis diurna <observed in co>nnection with the development of a <parasitic> fungus

Abstract of Paper read before section D— British Association, Exeter—

Specimens were produced of the common red campion, Lychnis diurna, infested with a parasitic fungus allied to the ``smut'' in wheat which fungus develops its fructification in the anthers of the flower. The campion in its ordinary healthy state has flowers bearing stamens only or pistils only, but about half the plants infested with the parasitic fungus bear flowers containing both stamens and pistils. The writer had never observed bisexual flowers on healthy plants, and attributed the occurrence of that condition in the specimens produced to the action of the parasitic fungus. The diseased plants very rarely produce seed but occasionally late in the season perfect capsules bearing good seed are found on them. A few of the flowers had been submitted to Mr. Darwin, and he had suggested that the pollen being destroyed by the parasite at an early period, the pistil was developed in compensation. But the writer thought that the influence exerted by the parasite was of a much more subtle and surprising character <than this,> and that instead of causing the develop<ment of> a pistil in compensation for destroyed <stamens the> fungus has the power to cause a plant which would naturally have produced pistils only to develope stamens for the accommodation of the parasite— She supposed that the spores of the fungus fell on the stigma of a healthy flower, and infected all the seeds produced by that capsule  that of the plants thus raised all which were naturally male plants remain unaffected in structure by the parasite, but they have their pollen destroyed by it— that all which were naturally female plants would develope their pistils to a certain extent, but as the fungus cannot produce spores without anthers to fructify in a pollen to feed on, it compels the campion to develope these for its accommodation, and the effort of so doing exhausts the forces of the plant, and causes the decay of the capsule, if indeed the previous stunting of the styles does not prevent fertilization. The production of healthy capsules late in the season may be owing to decay in the vigour of the fungus when, the pressure being removed, the plant resumes its natural functions. The fact that only about half the diseased plants are bisexual favours the view that the latter are female plants in which the growth of stamens has been induced by the presence of the fungus—